Life on Earth is based on a vast array of organic or carbon-based
compounds. All species of plants and animals use them for structure and
biological functioning.

Carbon is unique among the known elements. As a nonmetal, it forms
covalent bonds. A carbon atom can form four bonds, so it can combine
with several other atoms in many different ways, thereby yielding a
huge variety of diverse molecules.

Most chemicals known today are organic, and many of them are found
in nature. But chemists have also synthesized millions of organic
compounds not found in nature.

Chemists classify organic molecules according to the functional
groups they contain. A functional group is a specific combination of
bonded atoms that reacts in a characteristic and predictable way.

We'll use functional groups as a way of exploring the structure and
function of organic compounds. We'll start by learning the names and
formulas of some biologically important functional groups, then
consider the structure and function of food energy molecules and
nitrogen-containing molecules.

This activity includes a Reference Sheet about one class of
nitrogen-containing molecules, the amino acids. The Reference Sheet
will help you understand amino acid structures.